1. Field of the Invention
The present invention relates to a conductor module and an electromagnetic welding method for producing the conductor module. In particular, the conductor module is provided with a pair of flattened circuit that comprises a plurality of rectangular shaped conductors, and a pair of sheeted coverings disposed on both sides of the conductors. The conductors are joined together by application of electromagnetic welding.
2. Description of the Related Art
Usually, a variety of electronic devices are mounted to automobile as a vehicle. There is a wiring harness disposed in an automobile so as to deliver or transmit electricity from the battery of the electronic devices or control signal from a control device. The wiring harness is comprised of an electrical conduit, and a terminal fitting made of metallic plate and connected to the end portion of the electrical conduit. The electrical conduit is comprised of a core portion and a covering portion disposed on the core portion.
An automobile having multi-functionality has been continuously required. Accordingly, the number of electronic devices received in an automobile is continuously increasing. As a result, electrical conduits used in wiring harness correspondingly have a tendency to increase, and thus the mass and volume of the wiring harness is also increasing.
For the reasons set forth above, a flattened circuit (i.e., a flat circuit) such as a flat flexible cable (i.e., FFC) and a flexible printed circuit (i.e., FPC) have been proposed as the afore-mentioned electrical conduit for the wiring harness for the purpose of reduction in size and weight.
The flattened circuit includes a plurality of rectangular-shaped conductors and a pair of sheet-like covering disposed on both sides of the conductors, and is formed into a strip. The conductors are respectively linearly extended. The conductors are positioned in parallel with each other. The covering is configured to insulate one conductor from the other conductor.
In the afore-mentioned flattened circuit, the conductors are joined together by soldering. Soldering may adversely affect the flattened circuit in terms of durability and environment, and cause crack generation. Furthermore, due to the soldering portion, prepare cost also rises.
Otherwise, the conductors can be joined together by ultrasonic jointing and laser jointing. For more details, see Japanese Publication of Patent Application No. H11-192562. However, in the case of ultrasonic jointing and laser bonding, the conductors are joined together with the covering portion being left. In other words, (ultrasonic) energy is also applied to the covering portion. As a result, the covering portion may be damaged. For preventing the above damage, the covering portion must be partly eliminated. In this case, the electrical conduit is subject to corrosion, and thus electrical insulation may not be securely guaranteed.
Novel approach for joining conductors together has been proposed in Japanese Publication of Patent Application 2006-310016. In this document, the conductors are joined together while the covering portion remaining. The afore-mentioned method can be also designated as “electromagnetic welding method” which is thereafter described in detail. Referring to FIG. 11, each covering portion (103, 104) is eliminated from the each end portion of a pair of flattened circuits (101, 102) which are a part of conductor modules (1). As a result, one surface of the conductor (105) is completely exposed. Subsequently, one conductor is superposed to the other conductor such that the exposed surface of the one conductor (105) is in a closely contact with the exposed surface of the other conductor (105), as shown in FIG. 11. The superposed body thus obtained is disposed on a coil (106).
In this configuration the coil (106) and the conductor (105) are generally at right angles together in view of longitudinal direction, as shown in FIG. 12. In other words, the end portion of conductor (105) is disposed over the coil (106). In a case where electric current is applied to the coil (106) producing a magnetic field, excess current is generated in the area of the conductor (105). The magnetic flux generated in the area of the coil (106) and the magnetic flux generated in the area of the conductor (105) disposed adjacent to the coil (106) repel each other, and thus the conductor (105) disposed over the coil (106) has a tendency to move in a direction away from the coil (106) colliding the other conductor (105). High pressure generated in the event of collision allows the conductors to join together.
Meanwhile, in a case where the length of the exposed portion (L2) of the conductor (105) is less than the width of the coil (106), the conductors (105) would not join together. Accordingly, the length (L2) should be greater than the width of the coil (106). In this case, highly downsized and integrated circuit cannot be achieved.
To overcome above drawback, the coil (106) having smaller width and the conductor (105) having shorter exposed portion (L2) has been considered. However, the coil (106) having less width provides less heat capacity. In other words, when high current is applied to the coil (106), the coil (106) due to heat may be molten. Moreover, magnetic pressure generated in the event of joining the conductors together may easily deform the coil (106). Furthermore, according to prior art, all the conductors (105) disposed between the coverings (103, 104) are joined together. Accordingly, one drawback of prior art is that one cannot select the conductor (105) to be joined.
To overcome the afore-mentioned problems and drawbacks, there are provided an improved conductor module and magnetic pressure welding method capable of reducing or minimizing the joint area of the conductors.